The present invention relates to a heat conductive body for use in the heating of liquid by way of solar radiation incident on the conductive body, as well as to a water heater incorporating such a heat conductive body.
The present energy crisis has quickly become a world-wide problem of the most critical importance. It has been widely recognized that the use of petroleum as a major energy source must hereinafter decrease in the face of declining oil reserves. The development of alternative energy sources, such as nuclear power and the harnessing of natural phenonmenon for the production of energy, is accordingly becoming a matter of increasing urgency.
The present invention is directed to the provision of a heat conductive body which utilizes solar energy or radiation incident on the body to heat a liquid. The invention also contemplates use of the conductive body in a water heater of novel design.
Conventional heat conductive bodies comprise metallic plates having good thermal conductivity. Typically, the metal plate is heated by incident solar radiation and transmits its increased temperature to water flowing in contact therewith. The metal plate may, for example, be formed as a tube whereby the water flows through its interior. Various additional measures, such as the application of a thermally-conductive material to the exterior surface of the metal plate, are sometimes used to increase the absorption efficiency of the plate with respect to incident solar radiation.
It is well known that heat conductive bodies of metal plate suffer from a wide range of problems. The metal plate generally exhibits comparatively rapid oxidation and aging on its exterior faces due to the presence of impurities and moisture in the air. Corrosion is particularly problematical at weld points and develops all the more quickly as a result of the elevated temperature of the fast-moving liquid which is in virtually constant contact with the metal. The corrosion is thereby able to accumulate day-to-day, adversely affecting the heat conductivity of the metal plate and significantly decreasing its effective lifetime. It is also understood that the additional layer of heat absorption material applied to the surface of the metal plate is prone to peeling from the plate, thereby exposing such surface to rapid oxidation and consequent aging. Thus, the metal plate deteriorates from both of its opposite faces, being simultaneously oxidized by the air and corroded by the fast-moving contact liquid.